The products of the forest industry, e.g. lumber pieces, are customarily stored outdoors in piles for subsequent transportation. To keep lumber pieces relatively dry, bundles of lumber pieces are customarily covered to be protected from weathering. In order for some of the lumber inherent humidity to evaporate, bundles are often covered on five surfaces, leaving the bottom surface uncovered, whereby condensation may escape. Bundles have also been covered on their four lateral side faces, thereby leaving the bottom and top surface open, such that further humidity may escape. This latter four-face wrapping configuration is used with bundles placed under a roof and is also used to bond bundles of lighter material together, such as pallets of plastic components.
U.S. Pat. No. 3,809,223, issued on May 7, 1974 to Kendall discloses a five-face wrapping method wherein a inverted bag of heat shrinkable film is disposed on a bundle and is heated to tightly bond with the bundle. A moisture absorbent layer is disposed between the top surface of the bundle and the heat shrinkable film, whereby excess humidity is absorbed.
Canadian Patent Applications No. 2,198,201 and No. 2,230,026, both having a priority date of Feb. 21, 1997 disclose a frame having an expandable throat portion through which bundles pass while being displaced on a conveyor. A plastic tube having a closed end is disposed on the throat portion of the frame with the closed end placed downstream with respect to the conveyor such as to cover the opening defined by the throat portion. The tube portion is generally folded in accordion on the throat portion, which is expanded to stretch the plastic tube It is noted that the plastic tube consist of a plastic film stretchable and resilient at room temperature. As the bundle passes through the throat portion, the closed end of the plastic tube is caught by the front end of the bundle. As the bundle advances, the tube is gradually released from the throat portion, thereby tightly bonding to the bundle as it resiliently regains its shape. Once the bundle is downstream of the throat portion, a cutting and sealing apparatus cuts and seals the open end of the tube, thereby fully enclosing the bundle therein. It is noted that a corresponding Application has been awarded a patent, namely U.S. Pat. No. 6,161,365, issued on Dec. 19, 2000, to Girard et al. and discloses the method described above for hermetically bagging material such as lumber pieces. It is also observed that the step of disposing the plastic tube on the frame involves manual intervention.
Canadian Patent Applications No. 2,240,062 and No. 2,277,565 disclose a wrapping machine and a related method, which describe moveable arms which hold opposed ends of a plastic film. The arms are pivotally mounted in order to fold the plastic film on the four lateral side surfaces and the top surface of a bundle, thereby leaving the bottom surface uncovered. Each arm also comprises a stapling mechanism for securing the film to the bundle. These patent applications are fully automated.
The use of resilient plastic film is advantageous as it ensures a tight bonding with the bundled items. Heat shrinkable film provides a similar tight bonding, but involves heating means and is thus not as convenient and more costly. It appears that packaging with resilient plastic film provides a cost efficient method and desirable results. Thus, it would be desirable to apply these polymer properties with four or five face wrapping of bundles.